Structural and hyperfine properties of Mn and Co-incorporated akaganeites

The structural and hyperfine properties of pure and substituted akaganeites prepared in the presence of Mn, Co and urea are presented and discussed. In all samples, the chloride content increased with the increase in the urea concentration of the parent solution, and a small Mn-for-Fe or Co-for-Fe substitution occurred. In pure akaganeites, the increase of urea concentration provoked an enlargement of the unit cell volume and a decrease of the crystallinity of the synthesised oxides. The incorporation of Mn and Co provoked changes in cell parameters and an increase in the crystallinity of the samples. The hyperfine parameters for both iron sites of the akaganeites remained practically unchanged, and the spectral areas of the iron sites located close to the chlorides decreased for the doped samples. The recoilless f-factor increased for the substituted akaganeites, indicating an increase in the strength of the atomic bonding of the iron ions.